from kivy.app import App
from kivy.uix.label import Label
from kivy.animation import Animation

class MyApp(App):
    '''
    def build(self):
        return Label(text="Hello, Kivy!")
    '''
    def build(self):
        label = Label(text="Hello", font_size=72)
        anim = Animation(font_size=144, duration=2) + Animation(font_size=72, duration=2)
        anim.repeat = True
        anim.start(label)
        return label


if __name__ == "__main__":
    MyApp().run()